The main objective of the proposed study is to identify the sites and mechanisms of synthesis, assembly, and degradation of plasma membrane components, using the avian salt gland as a model system. A time course for the synthesis of plasma membrane components in general will be plotted for salt water induced plasma membrane amplification and, similarly, for removal of these components during subsequent fresh water induced plasma membrane reduction to determine the peak times for these events. The rates of protein and lipid synthesis will be determined by 3H-leucine and 3H-glycerol incorporation, and the Na,K-ATPase will serve as a specific plasma membrane protein marker. Ultrastructural changes in the gland secretory cells of possible relevance to plasma membrane synthesis and degradation will be observed. The specific activity and ultrastructural localization of various hydrolases will also be determined, especially during the period of removal of plasma membrane components. At the time of peak synthesis it is hoped that pulse chase experiments and autoradiography with 3H-precursors of protein and lipid will reveal the sites and mechanisms of plasma membrane synthesis and assembly. Attempts will be made to develop new cytochemical methods for localization of the Na,K-ATPase, by taking advantage of its reaction sequence and using ouabain derivatives. In addition, measurements of changes in specific RNA species and polysome profiles during plasma membrane synthesis should provide information on cellular control of the process. Other specific methods used will include: (1) measurement of Na,K-ATPase colorimetrically or by 3H-ouabain binding; (2) localization of the Na,K-ATPase by cytochemistry or 3H-ouabain autoradiography; (3) determination of changes in plasma membrane protein profiles by disc gel electrophoresis; (4) isolation of gland cells and plasma membrane fractions by enzyme digestion and cell fractionation techniques; (5) identification of RNA species by 3H-uridine incorporation and density gradient centrifugation; and (6) observation of polysome profiles using density gradient centrifugation.